This application claims the priority of Korean Patent Application No. 2002-709, filed Jan. 7, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a method of coding/decoding an image signal, and more particularly, to an optimal scanning method for transform coefficients in coding/decoding of an image or video.
2. Description of the Related Art
Image signals, e.g., images or videos, are compressed or coded according to the standards of moving picture expert group phase 1 (MPEG-1), MPEG-2, MPEG-4, H.261, H.263, or JPEG through a discrete cosine transform (hereinafter, referred to as “DCT”). Also, compressed or coded image signals are decoded through an inverse discrete cosine transform (hereinafter, referred to as “IDCT”). Selecting an optimal scanning method is a key point when trying to increase coding/decoding efficiency.
A scanning pattern described in U.S. Pat. No. 5,500,678 increases coding efficiency and is selected as a scanning pattern of MPEG-4 intra-coding. The scanning pattern of '678 uses a zigzag scanning pattern and a predefined scanning pattern.
Accordingly, the zigzag scanning pattern and the predefined scanning pattern are not efficient at coding all image signals. Also, since information on a selected scanning pattern should be coded with the image signals and provided to a decoder, the number of bits transmitted to the decoder increases. Further, the scanning pattern of '678 is predefined and thus there is a limit in selecting an optimal scanning pattern for various decoding blocks.
Scanning patterns described in U.S. Pat. No. 6,263,026 have a problem of reducing coding efficiency because a selected data word becomes too long if there are too many scanning patterns. Also, predefined finite scanning patterns used in '026 are not efficient in all image signals or data.